The team signed a number of veteran players - such as Andre Johnson, Frank Gore, Trent Cole, and Todd Herremans - with the hope that they could get another year or two of solid play out of them and that those moves would help put the Colts over the top in 2015. Obviously, that didn't happen. While the biggest factor in the Colts missing the playoffs entirely was Andrew Luck and his injuries, the team's offseason moves didn't really do much to help out either.
ESPN recently released their re-grade of each team's 2015 offseason, assessing each team's moves one year later. ESPN originally gave the Colts' moves a C-plus at the time last year, but that grade dropped significantly in the re-grade. In fact, the Colts were given a D-minus grade this time around, the same grade the Cleveland Browns and San Francisco 49ers got and ahead of only the Philadelphia Eagles, who received an F.
The Colts made a series of boom-or-bust moves that went bust. They still nearly won the AFC South, but they finally paid the price for failing to build an effective offensive line and scheme to protect quarterback Andrew Luck. With Luck struggling before finally leaving the lineup with a multitude of injuries, the Colts failed to maximize veteran offseason additions Frank Gore and Andre Johnson. They also had a hard time getting value from first-round receiver Phillip Dorsett, who missed five games entirely and played more than 35 percent of the snaps just once all season -- in Week 17.
The fact that the Colts got an awful grade in this re-grade shouldn't be surprising. The big moves that the Colts made, for the most part, fell way short of expectations. Andre Johnson caught 41 passes for 503 yards and four touchdowns, averaging 12.3 yards per catch and posting decent stats, but he wasn't a big factor on the field and was often invisible. For a guy who was supposed to be the reliable possession receiver, Johnson wasn't. Similarly, Trent Cole - signed for his pass rush ability - recorded just three sacks in 2015 to go along with 32 tackles, five tackles for loss, three passes defensed, and two forced fumbles. Todd Herremans entered the season as the Colts' starting left guard but was benched after just two games, and then he went from being a backup to an inactive player to, later in the season, being released altogether.
First round draft pick Phillip Dorsett also didn't have a big impact in 2015, either. He missed several games mid-season due to injury, and he caught just 18 passes for 225 yards and a touchdown all year. The Daily Norseman's Eric Thompson looked at the snap counts for each first round pick in 2015 and found that Dorsett played the seventh-fewest snaps of any first round pick (playing 212 snaps) - ahead of four players who missed the entire season and then two others. I think the Dorsett pick will look better in the years to come and so I don't think this pick was a failure (in fact, I think it looks better now than it did at the time), but without a doubt Dorsett wasn't a big factor in 2015 for the Colts.
It's hard to hold the struggles against Frank Gore, as he still managed to rush for 967 yards and six touchdowns while averaging 3.7 yards per carry behind a sub-par run-blocking line, and he also added 34 receptions for 267 yards and a touchdown. Gore did a good job with the Colts and had the best individual rushing season for any Colts player since 2007, and I don't necessarily think it's fair to hold Gore's numbers against him. Sure, maybe the Colts failed to maximize Gore's talent, but that says more about the surrounding cast (like playing behind that line and playing with a backup quarterback for nine games) than it does about Gore himself.
Other moves that weren't as heralded last offseason, however, turned out to be key for the Colts. Kendall Langford was tremendous in 2015 and looks to be a great signing. Henry Anderson was a home run draft pick, while David Parry started every game at nose tackle. Safety Dwight Lowery was a very good addition to the team's secondary as well. So the Colts did make several very good moves last offseason, but they weren't really the big-name ones, which is probably a big reason for the poor grade given by ESPN.